1. Field of the Invention
The present invention relates to antimicrobial polymer latexes and the antimicrobial coating, adhesive, sealant and elastomer (CASE) materials derived therefrom, wherein the polymer latex is derived from various monomers and antimicrobial quaternary ammonium ethylenically unsaturated compounds. These antimicrobial quaternary ammonium ethylenically unsaturated compounds are generally derived from ethylenically unsaturated sulfonic, phosphoric and/or carboxylic acids or salts thereof, and substantially saturated antimicrobial quaternary ammonium compounds. More specifically, the invention relates to improved antimicrobial polymer latexes and CASE materials, which possess prolonged antimicrobial activity, wherein the polymers and resulting CASE materials are produced using emulsion polymerization processes which utilize antimicrobial quaternary ammonium ethylenically unsaturated compounds derived from substantially saturated antimicrobial quaternary ammonium compounds and ethylenically unsaturated alkylsulfonic acids, alkylbenzene sulfonic acids, alkyl olefin sulfonic acids, alkyl alcohol sulfuric acid esters, or alkoxylated alkyl alcohol sulfuric acid esters, fatty acids, and fatty phosphate acid esters, or salts thereof, or mixtures thereof.
2. Description of the Related Art
The emulsion polymerization of ethylenically unsaturated monomers to form discrete solid polymeric particles for use in coating, adhesive, sealant, and/or elastomer (CASE) applications is well known to the art. Surfactants are commonly used materials in the manufacture of polymer latexes and various CASE products, such as, for example paints, printing inks, adhesives and pressure-sensitive adhesives. These surfactants are often indispensable for the manufacture and/or stabilization of these products in terms of processability. However, after such CASE products are used for coating, printing, adhesion or pressure bonding, the surfactants are no longer necessary, nor desirable. Rather, if the surfactant remains in the CASE product, the surfactant tends to adversely affect the resistance of the CASE material to water and even oil in many instances.
Surfactants for use in emulsion polymerization to form latexes, which are then used to prepare CASE materials, include traditional anionic surfactants, such as sodium dodecylbenzenesulfonate and nonionic surfactants such as polyoxyethylene nonylphenyl ether. However, CASE materials using polymer latex emulsions prepared using such traditional surfactants have the drawbacks of poor resistance to water and poor bond strength, typically because the surfactant remains in free form in the polymer latex and/or final CASE material. Additionally, these CASE materials often possess little or no antimicrobial activity, absent the addition of a separate antimicrobial material. When CASE materials are formulated to include such an antimicrobial material, the antimicrobial activity of the CASE material decreases realtively quickly with the passage of time and upon repeated exposure of the CASE material to various elements, including for example, water, washings with cleaning products, UV light, and the like.
CASE materials typically comprise, for example, paints (high-gloss, semi-gloss, and flat), caulks, and the like. CASE materials are typically applied to a variety of substrates, including for example, wood, metal, plastic, glass, ceramics, fiberglass, composite materials, cardboard, corrugated board, paper, textiles, non-woven materials, plastic, foam, tape or a combination thereof. Substrates can be virgin materials, i.e. materials which have not previously be treated or coated with a case material, or materials which have been previously coated or treated with a CASE material. CASE materials can be applied on top of or applied to a previously applied CASE material.
Conventional emulsion polymerization of ethylenically unsaturated monomers employs one or more surface active materials to emulsify the monomers and to stabilize the resulting polymer products, i.e., the latex. The monomers used in emulsion polymerization reactions are generally water-insoluble, but in some cases may be water-soluble. During a typical emulsion polymerization, a surfactant is used to suspend small portions of monomer in a continuous or semi-continuous aqueous phase. Typically, the monomer molecules are dispersed or suspended as small spheres in the aqueous phase, wherein the polymerization takes place within the small spheres. The surface active agents, i.e., surfactants, typically utilized in emulsion polymerization reactions are anionic, nonionic, and cationic surfactants or a mixture thereof.
The polymeric particles formed by the emulsion polymerization process are typically utilized to prepare coating, adhesive, sealant, and/or elastomer (CASE) materials. In a traditional emulsion polymerization reaction, the surfactant does not become chemically bonded to the polymeric particles by carbon-carbon bond formation, but rather remains absorbed on the polymeric particle product solution after the emulsion polymerization reaction is complete, i.e., once all of the monomer(s) is reacted. The unreacted surfactant can have a detrimental effect on the polymer product solution, as it can interfere with the performance of such polymerization products in CASE materials; the suspension of polymeric particles may become destabilized over time and undergo unwanted coagulation. In addition, the unreacted surfactant does not provide any desireable antimicrobial activity to the CASE material. The unreacted surfactant may cause unwanted peeling of a latex paint coating on a substrate, and decreased moisture and scrubability resistance in other various CASE applications. Residual surfactant can cause an undesirable "blooming" that leads to surface irregularities in a resulting CASE material that is applied to a substrate. Additionally, residual surfactant may lead to undesirable decreases in adhesion of a particular CASE material. The traditional surfactants act as stabilizers before, during, and after polymerization, but they typically have a detrimental effect on the properties of a dry latex film, for example, due to their tendency to migrate, i.e., to leave their original positions at the latex particle surfaces and form areas of higher concentration both in pockets within the film and at the film/air and film/substrate interfaces.
Several proposals have been made in the prior art to employ a polymerizable surfactant as the surface active agent during an emulsion polymerization reaction. U.S. Pat. No. 5,478,883 (incorporated herein by reference in its entirety) describes the use of ethylenically unsaturated polymerizable water-soluble nonionic surfactants formed by the reaction of a diallylamine compound with ethylene oxide, propylene oxide or butylene oxide, in emulsion polymerization reactions. Similarly, U.S. Pat. No. 5,162,475 (incorporated herein by reference) provides alpha-beta ethylenically unsaturated poly(alkylenoxy) polymerizable surface active compounds for use in emulsion polymerization. For additional examples of polymerizable surfactants for use in emulsion polymerization processes, see U.S. Pat. Nos. 4,377,185 and 4,049,608. Also see WO8912618, EP 747456 A2, and EP 770655 A2; all describing various ethylenically unsaturated surfactant approaches to producing CASE materials with reactive surfactants. However, none of these approaches have provided an alterative to improving the CASE material and at the same time, made the polymer latex and/or the resulting case material antimicrobial, i.e. resistant to bacteria, fungi, algae, viruses, and the like.
Non-polymerizable surfactant solutions to the traditional problems encountered in performing an emulsion polymerization process are numerous. U.S. Pat. No. 3,941,857 describes the use of epoxy resins which react with the residual anionic, cationic or nonionic surfactant. Polymerizable compounds such as allyl alcohol (and esters thereof) have been found to be ineffective due to the formation of undesirable high levels of coagulum in the final emulsion polymerization product. Additionally, see U.S. Pat. Nos. 4,224,455; 5,399,617; 4,075,411; 5,344,867; 5,296,627; 5,679,732, 5,536,811; 4,912,157; and 5,039,339; and WO 97/45495.
Quaternary ammonium salt formulations have been used as disinfectants for many years and these formulations have broad spectrum antimicrobial activity. These formulations are effecatious, at higher concentrations of quaternary ammonium salts, against certain gram positive and gram negative bacteria. These formulations have also been shown to show tuberculocidal activity. These formulations have been incorporated into latex formulations to prepare a blend of latex polymer particles and quaternary ammonium compounds, wherein the resulting formulation is applied to a substrate as a CASE material. These CASE materials and the substrates treated with the CASE materials often posses excellent initial antimicrobial activity. However, upon the passage of time, exposure to the elements, exposure to water, or repeated washings, the antimicrobial activity of the CASE and/or substrate decreases. This is generally due to a washing away or removal/leaching of the quaternary ammonium compounds present in the CASE material since these quaternary agents migrate to the surface.
It is known that on the surfaces of most substrates, micro-organisms develop grow, reproduce and or thrive. These micro organisms consist of a of organic materials, bacteria, algae, protozoa or other microorganisms, depending on the substrate and the type of exposure to the enviroment of the substrate. Numerous compounds termed biocides have been proposed and used for the treatment of such substrates to kill the micro organisms. Those most commonly employed in practice are halogens or halogenated inorganic or organic derivatives, such as chlorine, bromine, iodine, potassium chloride, hypochlorous acid and its sodium or calcium salts, hypobromous acid, the salts of dichloro- and trichloroisocyanuric acids, or halogenated hydantoins; however, these compounds have the disadvantage of being corrosive and of forming chlorinated compounds which are highly toxic. It has also been proposed to use peroxygenated derivatives, phenols and phenol derivatives, heavy metals or organic derivatives thereof, formaldehyde, benzoic acid and benzoates for treatments by contact with a substrate. However, many of these compounds are expensive, and/or they leave toxic or corrosive residues on the substrate. Generally, in order to be suitable for use in an appropriate fashion in a process for the treatment of microorganisms on a substrate, a biocidal compound must have the properties of: preventing the formation of the biological micro organisms, low toxicity to humans and animals that may come in contact with the biocidal compound and/or the substrate treated with such compounds, high fungicidal, algicidal and bactericidal activity.
Thus, there is a need for emulsion polymerization latexes and processes to prepare latexes comprising polymers and discrete polymeric particles that are well suited for use in antimicrobial CASE applications. There is a specific need for antimicrobial polymer latexes and CASE materials which comprise the polymer latex, wherein the final CASE material possess low water sensitivity, improved scrubability and/or improved adhesion properties. Additionally, improved antimicrobial CASE materials with prolonged antimicrobial activity, low animal toxicity, increased latex shear stability and lowered film yellowing tendencies are highly desirable. As will be more fully described hereinafter, it has been surprisingly discovered that incorporating antimicrobial quaternary ammonium compounds into the polymer latex particles by carbon-carbon bond formation provides an antimicrobial latex polymer which can subsequently be used to prepare antimicrobial CASE materials with prolonged antimicrobial activity, The antimicrobial activity remains even after the CASE materials and the substrates treated with the CASE materials are repeatedly exposured to the elements, exposured to water, or repeatedly washing many times; i.e., the antimicrobial activity of the CASE and/or substrate remains high for an extended period of time and there is generally no washing away or significant removal/leaching of the quaternary ammonium compounds present in the CASE material.